1. Field of the Invention
The present invention relates to an image display (a so-called plasma addressed electro-optical display) using plasma whereby to activate an electro-optical material layer so as to display an image.
2. Description of Prior Art
The resolution and contrast of a liquid-crystal type display unit have been improved by, for example, a so-called active matrix addressing method, in which an active device, such as a transistor, is provided for each display pixel and the active devices are operated.
The foregoing method, however, must use a multiplicity of semiconductor devices, such as thin-film transistors, thus causing a problem of unsatisfactory low manufacturing yield to arise when a display having a large area is manufactured. Thus, there arises a problem in that the cost cannot be reduced.
To solve the foregoing problem, a method has been suggested which employs discharge plasma active devices in place of the semiconductor devices, such as MOS transistors and thin-film transistors.
An image display apparatus (hereinafter called a "plasma addressed electro-optical display") has a stacked structure composed of a liquid crystal layer, which is an electro-optical material layer, and a plasma cell, in which plasma discharge takes place. A thin and dielectric-material plate made of glass and the like is disposed between the liquid crystal layer and the plasma cell.
The plasma addressed electro-optical display has a structure that the plasma cell is divided into linear plasma chambers by barrier ribs. The plasma chambers are sequentially switched and scanned, and signal voltages are synchronously applied to transparent electrodes opposite to the plasma chambers in such a manner that the liquid crystal layer is interposed. Thus, the liquid crystal layer is operated.
The plasma addressed electro-optical display is different from a usual plasma display in that a technical limit is imposed that the thin dielectric plate is frit-sealed to form the plasma cell (a discharge cell). Therefore, there arises a necessity that the frit seal and ends of the barrier ribs (ribs) are apart from each other for a short distance. To prevent undesirable discharge in the provided region, a structure is employed in which discharge electrodes in the foregoing region are covered with cover glass.
In this case, there is a tendency that the electric resistance values of the discharge electrodes under the cover glass are higher than those of discharge electrodes in regions which are not covered with the cover glass, that is, in an effective frame.
Therefore, the regions under the cover glass easily encounter problems, such as disconnection occurring attributable to heat. In particular, an aging process for stabilizing discharge sometimes encounters a sudden flow of a large electric current. The foregoing problem easily arises in the above-mentioned case.